In gas turbines as used for the generation of electrical energy in combined-cycle power stations or the like, in order to achieve favorable exhaust-gas values ("low NOx"), the procedure of spraying water into the associated combustion chamber together with the fuel (e.g. naphtha) is being increasingly adopted in order to reduce the temperature in the combustion chamber and thus prevent or make more difficult the formation of the undesirable nitrogen oxides. In large gas turbines, as manufactured, for example, by the applicant (e.g. of the type GT 13E2), a large, annular combustion chamber, in which a multiplicity of burners which can be activated individually are arranged (in an annular manner), is usually used for the combustion. Provided in this case for supplying the burners with the fuel and the water are burner lances which are each interchangeable and in whose interior space fuel and water and, if need be, also a pilot gas are fed in from outside to the burners. Here, fuel and water may be carried in separate lines and sprayed in separately, or may already be mixed at the entry to the lance to form an emulsion, which is then transmitted in a common line (in this respect see DE-A1-44 01 097 of the applicant).
In all cases, the burner lances are connected in each case at the entry side via separate feed-line valves to a fuel feed line and a water feed line, which are directed past the lance entries (lance heads) in an annular manner in order to supply all the lances. The feed-line valves permit the starting and shutdown of individual burners and at the same time control the mixture ratio of fuel to water. A further valve which connects the two feed lines to one another permits flushing of the fuel feed line by means of water from the water feed line. In addition, a venting valve is provided on the fuel ring main, and air (or water) located in the system can escape through this venting valve when the ring main is being filled with fuel.
Such a fuel distribution system accordingly has a number of valves which amount to a multiple of the number of burners or lances. Since each of these valves contains movable parts, in particular the susceptibility to faults and the maintenance costs, in addition to the plant costs, increase with the number of valves. In addition, individual activation of the valves requires complicated wiring and control logic.